Radio-phonograph adapter



Oct. 13, 1953 T. F. THOMPSON RADIO-PHONOGRAPH ADAPTER Filed April 12,1950 INVENTOR. T homes/'2' Hwmpson Fatentecl Oct. 13, 1953 UNITED STATESPATENT OFFICE RADIo-PHoNoGRAPI-I ADAPTER Thomas F. Thompson, Eugene;0reg., assignor of one-third to Dale Belford'and one-third to Oliver D.Olson, both of Portland, 0reg., and one-sixth to Richard B. Thompson,Eugene,

Oreg.

Application April I2, 1950, SeriaINo. 155,529

12 Claims; (01. 179--100.11)

This invention pertains to radio-phonographof the type described residesin the fact that substantial' modification of the-radio: receiver isnecessary in order to couple the record playerthereto. For example,theprevailing practice comprises the installation at the back of thereceiver of a switch by which to disconnect temporarily the stagespreceding the audio amplifier. A phono jack is also. installed at theback of the receiver to accommodate releasable attachment of the recordplayer. These and other similar modifications represent a considerablecost to the owner of the radio.

It is a principal object of the present invention to provide an adapter:by which. aradio and a record player may be interconnected detaehablymerely by interposing anv adapter plugbetween the audio amplifier tubeand its socket base.

Another important object of thisinvention is the provision of aradio-phonograph: adapter which includes control-means for varyingthevol ume of phonograph reception" independently of. the radio broadcastvolumecontrol.

A further important object of this invention is to provide aradio-phonograph adapter which in-- cludes means by which the grid biasestablished in the audio circuit of the radio receiver is maintainedwhen the adapter is in operation.

A further object is the provision of an adapter for detachablyinterconnecting a record player and a radio receiver, said; adapterbeing con-- structed in such manner as to permit the use ofthe radioreceiver for conventional broadcast reception withoutdisconnecting theadapter therefrom and without. impairing or otherwise disturbing thefidelity, volume, or other actions and qualities characteristic of theradio receiver per so.

A still further object is the provision of a portable radio-phonographadapter which is of simplified construction for economical productionandwhich affords maximum fidelity of phonograph reception.

Th audio amplifying sys The- A further general object of thisinvention-is to provide a novel electrical circuit by which tointerconnect asignal generator andan amplifier. These and other objectsand advantages oithe present invention will appear. from the followingdetailed description taken in connection with the accompanying drawing,in which:

Figure 1 is a schematic diagram showing the electrical circuitembodyingthe present invention 3 and illustrating the mannerin which the.sameis arranged for coupling together" a. radio receiver and a recordplayer;

Figure 2 is a fragmentary perspective View showing'a container in whichthe electrical circuit ofthis invention ishoused for use as a portableadapter; and

Figur 3 is a fragmentary perspective view of a tube adapter plugemployedin the present invention.

Stated broadly, the present invention comprises. an electrical circuitarranged detachably to interconnect the output of a record player withthe grid and cathode elements of theinput audio tube of theaudio-amplifier ofa radio receiver.

Referring to the drawing, the adapter plug. I selected for a particularinstallation must correspond with thetype of audio amplifier tube 2; andits complementary socket base 3; Sincevarious types of audio tubes arepresentlyuse'd in diverse makes of" radio receivers, it is. necessarythat various types of adapter plugs be provided; In.

any: event, the. adapter plug l is provided with female sockets. tproportioned; and arranged to. receive the male contacts 5 extending.from the: base of. the audio tube 2; A-central hole Shaving an offsetgroove 7 is also provided in the female end of the adapter plug toreceive the complementary shaped central positioning stud of tube 2, inmanner well-known. in theart. Positioning means other than the centralholeand stud illustrated are also well-known. For example, varioustypesof miniature tubes are provided with 0011- tact prongs eitherofpolarized shape. or position;

The type ofv tube base and socket base used: is im material, and. doesnot form a part of this invention..

The end of adapter plug opposite the female sockets 4 is provided withmale contactsfii which correspond in position With said sockets 4'; Themale contacts 8" also I correspond in position with the female sockets 9of the audio-tube socket base 3. A central positioning stud. I0 is alsoprovided in the adapter plug l for reception-in a complementary'holeprovided in the socket base 3.

Referring now particularly to Figure I of the drawing, the principalelements of the audio amplifier tube 2 are shown to consist of a platell, grid I2, cathode I3 and heater element I4. The female socket 4 andits complementary male contact 8 for the plate II are interconnected byan electrical lead I5. In similar manner the complementary female andmale connections for the cathode I3 are interconnected by lead E5.

The female socket 4 complementing the male contact 5 for the grid I2 isconnected by lead I1 to the adjustable contact I8 of the variableresistor I9 which functions as a volume control in the manner describedhereinafter. The male contact 8 complementing the female socket 4 forgrid I2 is connected by lead 20 to one end of the variable resistor I9.

The end of resistor I9 opposite the connection of lead 20 is connectedthrough coupling condenser 2| to the central contact 22 of a phono jack.The outer contact 23 of the phono jack is connected through bypasscondenser 24 to one side of switch 25. The opposite side of switch 25 isconnected to the end of variable resistor I9 to which the lead 20 issecured. Said switch is preferably of the type which is incorporated atthe low volume end of the volume control resistor I9 and is actuated bythe volume control knob 26 shown in Figure 2. Accordingly, the switch 25and resistor I9 are shown interconnected by the dotted line 21. Theouter contact 23 of the phono jack is also connected electrically to thelead I6 of the cathode I3 by means of lead 28.

The inner and outer female contacts 22 and 23,

respectively, of the phono jack are proportioned and arranged to receivethe complementary inner and outer male contacts of a phono jack fordetachable connection therewith. Said inner and outer male contacts areconnected, respectively, by leads 29 and 30 to the output of the recordplayer. For purposes of illustration, the output of the record player isshown to comprise a piezoelectric crystal 3|.

It is to be observed that coupling condenser 2| and the terminalcontacts 22, 23 form a series combination, and that bypass condenser 24and switch 25 form a second series combination. Bypass condenser 24 andterminal contact 23 are connected to the cathode I3 through lead 28.Coupling condenser 2| and switch 25 are connected together throu hvariable resistor volume control I9, and the movable contact I8 of saidvolume control is connected to grid l2 through lead I1. Thus, the saidtwo series combinations are connected in parallel at one end throughvolume control I9 and its movable contact II! to grid l2 and at theopposite end to cathode I3.

Referring now to Figure 2 of the drawing, the female contacts 22 and 23of the phono jack, the coupling condenser 2|, the bypass condenser 24and the variable resistor I9 and switch 25 are mounted in a small box32. Said box is indicated in dotted outline in Figure l. The phono jackprojects through the upper face of the box, as shown, for convenience inconnecting the record player. The volume control knob is secured to theadjustable contact I8 of the variable resistor I9 to facilitateadjustment of the latter, as indicated hereinbefore.

The wires I1 and 20 leading from the adjustable contact IB and variableresistor I9, respectively, are preferably separately encased in rubber34 and then covered with metallic shielding 35. The two shielded wiresare then enclosed together in a fabric or other type of covering 36.

4 The shield 35 of one of the wire leads is utilized as electrical lead28 which interconnects the cathode I3 and the outer female contact 23 ofthe phono jack.

Although the circuit elements described hereinbefore may vary inaccordance with specific installations, the values chosen for thecircuit illustrated are as follows: Coupling condenser 2| is 0.01microfarad; bypass condenser 24 is 0.1 microfarad; and the variableresistor I9 is one megohm.

The installation and operation of the adapter embodying the presentinvention is as follows: The audio amplifier tube 2 is first removedfrom its socket base 3. The male contacts 8 of the adapter plug I, whichcorresponds to the type of audio amplifier tube provided in thereceiver, is then inserted in the socket base 3. The male contacts 5 ofthe audio tube 2 are now inserted in the female sockets 4 of the adapterplug, whereby the adapter plug I becomes interposed between the tube 2and its socket base 3.

With the adapter plug I installed as described and the volume controlknob 26 turned to the off position, i. e. with contact I8 at the extremeleft of resistor I9 as shown in Figure l and switch open, the radioreceiver may be used in conventional manner for broadcast reception. Itis to be noted that, in this position of the volume control knob 26, theseries combination of variable resistor I9, coupling condenser 2| andthe crystal pickup 3| are placed in shunt across the grid resistor 31provided in the radio receiver. The resistance of said seriescombination is of such high magnitude as to effect very little change inthe characteristic grid resistance 31 of the receiver. Moreover, theresistances of the volume control resistor I9 and the crystal pickup aresuch as to reduce the effective capacitance of the coupling condenser 2|to such a small value that the slight attenuation of high audiofrequencies thereby produced is of no consequence. Thus, it is apparentthat the radio receiver may be used for conventional broadcast receptionwithout detaching the adapter of the present invention and without lossof fidelity and other qualities inherent in the receiver per se.

When it is desired to use the radio receiver for amplifying the soundsignal of the record player, the volume control of the receiver may beturned down, if desired, and knob 26 of the adapter is turned to theposition at which swtich 25 becomes closed. With switch 25 closed,bypass condenser 24 becomes placed in shunt across the grid resistor 31of the input audio tube of the radio receiver audio amplifier. Theimpedance of said grid resistor 31 is reduced to a low value and thevolume control resistor I9 becomes the entire grid load. The electricalenergy developed, for example, in the crystal pickup 3| of the recordplayer is thereby passed to the audio amplifier through the couplingcondenser 2| and volume control resistor I9. Coupling condenser 2|functions primarily to isolate the grid bias voltage from the crystal 3|and to prevent damage to the crystal in the event that the adapter I isplaced accidentally in the wrong tube socket. The coupling condenserfunctions additionally to filter out undesirable needle noise and otherdisturbances from the record player.

From the foregoing description it will be apparent that the presentinvention provides a device of simplified and economical construction bywhich a radio receiver and a record player may be interconnected withrapidity and ease,

aces-see Modification of the radio: receiver; asrequired heretofore, isobviated completely, with the resultthat various modificationsmay bemadein the structure described hereinbefore without departing from thescope and spirit of this invention. For example, if the circuitdescribed hereir ibe'fore' is to be used with the'type'ofamplifier-which operates in Class A with the cathode and grid at equalpotentials, the coupling condenser 2| may be omitted if desired. Itsinclusion in the circuit under this condition is not detrimental,however. As a second example, the device may function with equalfacility to couple any type of signal generator to acorrespondingamplifier merely by selecting the proper valuesof circuit elements.Anillustration of such use is the coupling of an electrical musicalinstrument to an audio amplifier. When used for this purpose, manyplayers prefer to turn the control Hi to full volume and then regulatethe volume from the controlprovided onthemusical instrument. In thesecases it is apparent that the volume control [9 may be replaced by afixed resistance. It is also apparent that the adapter circuit describedhereinbefore may be incorporated as an integral part of either a radioreceiver or a record player, rather than forming a unit detachable fromsaid receiver and record player. It is intended, therefore, that theforegoing description is primarily illustrative and is not to beconstrued in a limiting sense.

Having thus described my invention and the manner in which the same maybe used, what I claim as new and desire to secure by Letters Patent is:

1. An adapter for detachably interconnecting a signal generator and anamplifier wherein said amplifier includes a cathode and a grid circuit,said adapter comprising a resistance, a bypass condenser, terminal meansfor connecting the output of the signal generator, and means fordetachably connecting at least part of the resistance in series in thegrid circuit to amplify the generated signal and for detachablyconnecting the bypass condenser and the terminal means between thecathode and grid circuit at opposite ends of the series portion of theresistance.

2. An adapter for detachably interconnecting a signal generator and anamplifier wherein said amplifier includes a cathode and a grid circuit,said adapter comprising a resistance, a bypass condenser, the seriescombination of a coupling condenser and terminal means for connectingthe output of the signal generator, and means for detachably connectingat least part of the resistance in series in the grid circuit to amplifythe generated signal and for detachably connecting the bypass condenserand the series combination between the cathode and grid circuit atopposite ends of the series portion of the resistance.

3. An adapter for detachably interconnecting a signal generator and anamplifier wherein said amplifier includes a cathode and a grid circuit,said adapter comprising a resistance, the series combination of a switchand a bypass condenser, terminal means for connecting the output of thesignal generator, and means for detachably connecting at least part ofthe resistance in series in the grid circuit to amplify the generatedsignal and for detachably connecting the bypass condenser and theterminal means between the cathode and grid circuit-atopposite ends: ofthe;

seriesportion of thdresistance.

4. An adapter for detachably interconnecting:

a signal generator and an amplifier wherein said amplifier includes acathode and a grid: circuit, said adapter comprising a resistance, theseries combination of a switch and a bypass condenser, theseriescombination of acoupling condenser and terminal means for connecting theoutput of the signal'gen'erator, and means for detachably connecting atleastpartof theresistance in series the grid circuit. to amplifythegenerated signal and for detachably connecting the respective, seriescombinations between the cathode and grid circuit at. opposite ends ofthe series portion of the resistance.

5; An adapter for detachably interconnecting:

a signal generator and an amplifier wherein said.

amplifier includes a cathode circuit, a: grid circuit, an amplifier tubeand tube base, said adapter comprising a resistance, a bypass condenser,ter' minalmeans for connecting the output of the signal generator, andadapter plug means proportioned' and arranged to be interposed be.-tween said amplifier tube and. tube base for detachably connecting atleast part of the resistance in series in the grid circuit to amplifythe generated signal and for detachably connecting the bypass condenserand the terminal means between the cathode and grid circuit at oppositeends of the series portion of the resistance.

6. The adapter of claim 4 wherein the signal generator is a recordplayer, the amplifier is the audio amplifier of a radio receiver, andthe resistance is a volume control.

7. An adapter for detachably interconnecting a record player and theaudio amplifier of a radio receiver wherein said amplifier includes acathode circuit, a grid circuit, an amplifier tube and tube base, saidadapter comprising a potentiometer volume control, the seriescombination of a switch and a bypass condenser, the series combinationof a coupling condenser and terminal means for connecting the output ofthe record player, and adapter plug means proportioned and arranged tobe interposed between said amplifier tube and tube base for detachablyconnecting at least part of the volume control in series in the gridcircuit to amplify the record player signal and for detachablyconnecting the respective series combinations between the oathode andgrid circuit at opposite ends of the series portion of the volumecontrol.

8. In combination with an alternating current signal generator and aradio receiver having an audio amplifier wherein said amplifier includesa cathode and a grid circuit; a resistance, at least part of theresistance being connected in series in the grid circuit for amplifyingthe generated signal, and a radio signal bypass condenser connectedbetween the cathode and grid circuit at one end of the series portion ofthe resistance, the output of the signal generator being connectedbetween the cathode and grid circuit at the opposite end of the seriesportion of the resistance.

9. In combination with an alternating current signal generator and aradio receiver having an audio amplifier wherein said amplifier includesa cathode and a grid circuit; a resistance, at least part of theresistance being connected in series in the grid circuit for amplifyingthe generated signal, a radio signal bypass condenser connected betweenthe cathode and grid circuit at one end of the series portion of theresistance,

accused and the series combination of a coupling condenser and theoutput of the signal generator connected between the cathode and gridcircuit at the opposite end of the series portion of the resistance.

10. In combination with a signal generator and a radio receiver havingan audio amplifier wherein said amplifier includes a cathode and a gridcircuit; a resistance, at least part of the resistance being connectedin series in the grid circuit for amplifying the generated signal, andthe series combination of a switch and a radio signal bypass condenserconnected between the cathode and grid circuit at one end of the seriesportion of the resistance, the output of the signal generator beingconnected between the cathode and grid circuit at the opposite end ofthe series portion of the resistance.

11. In combination with a signal generator and a radio receiver havingan audio amplifier wherein said amplifier includes a cathode and a gridcircuit; a resistance, at least part of the resistance being connectedin series in the grid circuit for amplifying the generated signal, theseries combination of a switch and a radio signal bypass condenserconnected between the cathode and grid circuit at one end of the seriesportion of the resistance, and the series combination of a couplingcondenser and the output or the signal generator connected between thecathode and grid circuit at the opposite end of the series portion ofthe resistance.

12. The combination of claim 11 wherein the signal generator is a recordplayer, the amplifier is the audio amplifier of a radio receiver, andthe resistance is a volume control.

THOMAS F. THOMPSON.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,681,897 Goudy Aug. 21, 1928 1,852,424 Leishman Apr. 5, 19321,896,550 Minz Feb. 7, 1933 1,934,498 Guedon Nov. 9, 1933 1,959,272Leishman May 15, 1934 2,107,416 Huth Feb. 8, 1938 2,109,256 Sparks Mar.1, 1938 2,539,674 Rhoads Jan. 30, 1951

